1 /* 2 * Copyright (c) 1997, 2016, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/stringTable.hpp" 27 #include "classfile/symbolTable.hpp" 28 #include "classfile/systemDictionary.hpp" 29 #include "code/codeCache.hpp" 30 #include "code/icBuffer.hpp" 31 #include "code/nmethod.hpp" 32 #include "code/pcDesc.hpp" 33 #include "code/scopeDesc.hpp" 34 #include "gc/shared/collectedHeap.hpp" 35 #include "gc/shared/gcLocker.inline.hpp" 36 #include "interpreter/interpreter.hpp" 37 #include "logging/log.hpp" 38 #include "memory/resourceArea.hpp" 39 #include "memory/universe.inline.hpp" 40 #include "oops/oop.inline.hpp" 41 #include "oops/symbol.hpp" 42 #include "oops/valueKlass.hpp" 43 #include "runtime/atomic.hpp" 44 #include "runtime/compilationPolicy.hpp" 45 #include "runtime/deoptimization.hpp" 46 #include "runtime/frame.inline.hpp" 47 #include "runtime/interfaceSupport.hpp" 48 #include "runtime/mutexLocker.hpp" 49 #include "runtime/orderAccess.inline.hpp" 50 #include "runtime/osThread.hpp" 51 #include "runtime/safepoint.hpp" 52 #include "runtime/signature.hpp" 53 #include "runtime/stubCodeGenerator.hpp" 54 #include "runtime/stubRoutines.hpp" 55 #include "runtime/sweeper.hpp" 56 #include "runtime/synchronizer.hpp" 57 #include "runtime/thread.inline.hpp" 58 #include "runtime/timerTrace.hpp" 59 #include "services/runtimeService.hpp" 60 #include "trace/tracing.hpp" 61 #include "trace/traceMacros.hpp" 62 #include "utilities/events.hpp" 63 #include "utilities/macros.hpp" 64 #if INCLUDE_ALL_GCS 65 #include "gc/cms/concurrentMarkSweepThread.hpp" 66 #include "gc/g1/suspendibleThreadSet.hpp" 67 #endif // INCLUDE_ALL_GCS 68 #ifdef COMPILER1 69 #include "c1/c1_globals.hpp" 70 #endif 71 72 // -------------------------------------------------------------------------------------------------- 73 // Implementation of Safepoint begin/end 74 75 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; 76 volatile int SafepointSynchronize::_waiting_to_block = 0; 77 volatile int SafepointSynchronize::_safepoint_counter = 0; 78 int SafepointSynchronize::_current_jni_active_count = 0; 79 long SafepointSynchronize::_end_of_last_safepoint = 0; 80 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE 81 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only 82 static bool timeout_error_printed = false; 83 84 // Roll all threads forward to a safepoint and suspend them all 85 void SafepointSynchronize::begin() { 86 EventSafepointBegin begin_event; 87 Thread* myThread = Thread::current(); 88 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint"); 89 90 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 91 _safepoint_begin_time = os::javaTimeNanos(); 92 _ts_of_current_safepoint = tty->time_stamp().seconds(); 93 } 94 95 #if INCLUDE_ALL_GCS 96 if (UseConcMarkSweepGC) { 97 // In the future we should investigate whether CMS can use the 98 // more-general mechanism below. DLD (01/05). 99 ConcurrentMarkSweepThread::synchronize(false); 100 } else if (UseG1GC) { 101 SuspendibleThreadSet::synchronize(); 102 } 103 #endif // INCLUDE_ALL_GCS 104 105 // By getting the Threads_lock, we assure that no threads are about to start or 106 // exit. It is released again in SafepointSynchronize::end(). 107 Threads_lock->lock(); 108 109 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); 110 111 int nof_threads = Threads::number_of_threads(); 112 113 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads); 114 115 RuntimeService::record_safepoint_begin(); 116 117 MutexLocker mu(Safepoint_lock); 118 119 // Reset the count of active JNI critical threads 120 _current_jni_active_count = 0; 121 122 // Set number of threads to wait for, before we initiate the callbacks 123 _waiting_to_block = nof_threads; 124 TryingToBlock = 0 ; 125 int still_running = nof_threads; 126 127 // Save the starting time, so that it can be compared to see if this has taken 128 // too long to complete. 129 jlong safepoint_limit_time = 0; 130 timeout_error_printed = false; 131 132 // PrintSafepointStatisticsTimeout can be specified separately. When 133 // specified, PrintSafepointStatistics will be set to true in 134 // deferred_initialize_stat method. The initialization has to be done 135 // early enough to avoid any races. See bug 6880029 for details. 136 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 137 deferred_initialize_stat(); 138 } 139 140 // Begin the process of bringing the system to a safepoint. 141 // Java threads can be in several different states and are 142 // stopped by different mechanisms: 143 // 144 // 1. Running interpreted 145 // The interpreter dispatch table is changed to force it to 146 // check for a safepoint condition between bytecodes. 147 // 2. Running in native code 148 // When returning from the native code, a Java thread must check 149 // the safepoint _state to see if we must block. If the 150 // VM thread sees a Java thread in native, it does 151 // not wait for this thread to block. The order of the memory 152 // writes and reads of both the safepoint state and the Java 153 // threads state is critical. In order to guarantee that the 154 // memory writes are serialized with respect to each other, 155 // the VM thread issues a memory barrier instruction 156 // (on MP systems). In order to avoid the overhead of issuing 157 // a memory barrier for each Java thread making native calls, each Java 158 // thread performs a write to a single memory page after changing 159 // the thread state. The VM thread performs a sequence of 160 // mprotect OS calls which forces all previous writes from all 161 // Java threads to be serialized. This is done in the 162 // os::serialize_thread_states() call. This has proven to be 163 // much more efficient than executing a membar instruction 164 // on every call to native code. 165 // 3. Running compiled Code 166 // Compiled code reads a global (Safepoint Polling) page that 167 // is set to fault if we are trying to get to a safepoint. 168 // 4. Blocked 169 // A thread which is blocked will not be allowed to return from the 170 // block condition until the safepoint operation is complete. 171 // 5. In VM or Transitioning between states 172 // If a Java thread is currently running in the VM or transitioning 173 // between states, the safepointing code will wait for the thread to 174 // block itself when it attempts transitions to a new state. 175 // 176 { 177 EventSafepointStateSynchronization sync_event; 178 int initial_running = 0; 179 180 _state = _synchronizing; 181 OrderAccess::fence(); 182 183 // Flush all thread states to memory 184 if (!UseMembar) { 185 os::serialize_thread_states(); 186 } 187 188 // Make interpreter safepoint aware 189 Interpreter::notice_safepoints(); 190 191 if (DeferPollingPageLoopCount < 0) { 192 // Make polling safepoint aware 193 guarantee (PageArmed == 0, "invariant") ; 194 PageArmed = 1 ; 195 os::make_polling_page_unreadable(); 196 } 197 198 // Consider using active_processor_count() ... but that call is expensive. 199 int ncpus = os::processor_count() ; 200 201 #ifdef ASSERT 202 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 203 assert(cur->safepoint_state()->is_running(), "Illegal initial state"); 204 // Clear the visited flag to ensure that the critical counts are collected properly. 205 cur->set_visited_for_critical_count(false); 206 } 207 #endif // ASSERT 208 209 if (SafepointTimeout) 210 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS; 211 212 // Iterate through all threads until it have been determined how to stop them all at a safepoint 213 unsigned int iterations = 0; 214 int steps = 0 ; 215 while(still_running > 0) { 216 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 217 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended"); 218 ThreadSafepointState *cur_state = cur->safepoint_state(); 219 if (cur_state->is_running()) { 220 cur_state->examine_state_of_thread(); 221 if (!cur_state->is_running()) { 222 still_running--; 223 // consider adjusting steps downward: 224 // steps = 0 225 // steps -= NNN 226 // steps >>= 1 227 // steps = MIN(steps, 2000-100) 228 // if (iterations != 0) steps -= NNN 229 } 230 if (log_is_enabled(Trace, safepoint)) { 231 ResourceMark rm; 232 cur_state->print_on(Log(safepoint)::trace_stream()); 233 } 234 } 235 } 236 237 if (iterations == 0) { 238 initial_running = still_running; 239 if (PrintSafepointStatistics) { 240 begin_statistics(nof_threads, still_running); 241 } 242 } 243 244 if (still_running > 0) { 245 // Check for if it takes to long 246 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { 247 print_safepoint_timeout(_spinning_timeout); 248 } 249 250 // Spin to avoid context switching. 251 // There's a tension between allowing the mutators to run (and rendezvous) 252 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that 253 // a mutator might otherwise use profitably to reach a safepoint. Excessive 254 // spinning by the VM thread on a saturated system can increase rendezvous latency. 255 // Blocking or yielding incur their own penalties in the form of context switching 256 // and the resultant loss of $ residency. 257 // 258 // Further complicating matters is that yield() does not work as naively expected 259 // on many platforms -- yield() does not guarantee that any other ready threads 260 // will run. As such we revert to naked_short_sleep() after some number of iterations. 261 // nakes_short_sleep() is implemented as a short unconditional sleep. 262 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping 263 // can actually increase the time it takes the VM thread to detect that a system-wide 264 // stop-the-world safepoint has been reached. In a pathological scenario such as that 265 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe. 266 // In that case the mutators will be stalled waiting for the safepoint to complete and the 267 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread 268 // will eventually wake up and detect that all mutators are safe, at which point 269 // we'll again make progress. 270 // 271 // Beware too that that the VMThread typically runs at elevated priority. 272 // Its default priority is higher than the default mutator priority. 273 // Obviously, this complicates spinning. 274 // 275 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0). 276 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will. 277 // 278 // See the comments in synchronizer.cpp for additional remarks on spinning. 279 // 280 // In the future we might: 281 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning. 282 // This is tricky as the path used by a thread exiting the JVM (say on 283 // on JNI call-out) simply stores into its state field. The burden 284 // is placed on the VM thread, which must poll (spin). 285 // 2. Find something useful to do while spinning. If the safepoint is GC-related 286 // we might aggressively scan the stacks of threads that are already safe. 287 // 3. Use Solaris schedctl to examine the state of the still-running mutators. 288 // If all the mutators are ONPROC there's no reason to sleep or yield. 289 // 4. YieldTo() any still-running mutators that are ready but OFFPROC. 290 // 5. Check system saturation. If the system is not fully saturated then 291 // simply spin and avoid sleep/yield. 292 // 6. As still-running mutators rendezvous they could unpark the sleeping 293 // VMthread. This works well for still-running mutators that become 294 // safe. The VMthread must still poll for mutators that call-out. 295 // 7. Drive the policy on time-since-begin instead of iterations. 296 // 8. Consider making the spin duration a function of the # of CPUs: 297 // Spin = (((ncpus-1) * M) + K) + F(still_running) 298 // Alternately, instead of counting iterations of the outer loop 299 // we could count the # of threads visited in the inner loop, above. 300 // 9. On windows consider using the return value from SwitchThreadTo() 301 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions. 302 303 if (int(iterations) == DeferPollingPageLoopCount) { 304 guarantee (PageArmed == 0, "invariant") ; 305 PageArmed = 1 ; 306 os::make_polling_page_unreadable(); 307 } 308 309 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or 310 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus) 311 ++steps ; 312 if (ncpus > 1 && steps < SafepointSpinBeforeYield) { 313 SpinPause() ; // MP-Polite spin 314 } else 315 if (steps < DeferThrSuspendLoopCount) { 316 os::naked_yield() ; 317 } else { 318 os::naked_short_sleep(1); 319 } 320 321 iterations ++ ; 322 } 323 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long"); 324 } 325 assert(still_running == 0, "sanity check"); 326 327 if (PrintSafepointStatistics) { 328 update_statistics_on_spin_end(); 329 } 330 331 if (sync_event.should_commit()) { 332 sync_event.set_safepointId(safepoint_counter()); 333 sync_event.set_initialThreadCount(initial_running); 334 sync_event.set_runningThreadCount(_waiting_to_block); 335 sync_event.set_iterations(iterations); 336 sync_event.commit(); 337 } 338 } //EventSafepointStateSync 339 340 // wait until all threads are stopped 341 { 342 EventSafepointWaitBlocked wait_blocked_event; 343 int initial_waiting_to_block = _waiting_to_block; 344 345 while (_waiting_to_block > 0) { 346 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block); 347 if (!SafepointTimeout || timeout_error_printed) { 348 Safepoint_lock->wait(true); // true, means with no safepoint checks 349 } else { 350 // Compute remaining time 351 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos(); 352 353 // If there is no remaining time, then there is an error 354 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) { 355 print_safepoint_timeout(_blocking_timeout); 356 } 357 } 358 } 359 assert(_waiting_to_block == 0, "sanity check"); 360 361 #ifndef PRODUCT 362 if (SafepointTimeout) { 363 jlong current_time = os::javaTimeNanos(); 364 if (safepoint_limit_time < current_time) { 365 tty->print_cr("# SafepointSynchronize: Finished after " 366 INT64_FORMAT_W(6) " ms", 367 ((current_time - safepoint_limit_time) / MICROUNITS + 368 (jlong)SafepointTimeoutDelay)); 369 } 370 } 371 #endif 372 373 assert((_safepoint_counter & 0x1) == 0, "must be even"); 374 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 375 _safepoint_counter ++; 376 377 // Record state 378 _state = _synchronized; 379 380 OrderAccess::fence(); 381 382 if (wait_blocked_event.should_commit()) { 383 wait_blocked_event.set_safepointId(safepoint_counter()); 384 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block); 385 wait_blocked_event.commit(); 386 } 387 } // EventSafepointWaitBlocked 388 389 #ifdef ASSERT 390 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 391 // make sure all the threads were visited 392 assert(cur->was_visited_for_critical_count(), "missed a thread"); 393 } 394 #endif // ASSERT 395 396 // Update the count of active JNI critical regions 397 GCLocker::set_jni_lock_count(_current_jni_active_count); 398 399 if (log_is_enabled(Debug, safepoint)) { 400 VM_Operation *op = VMThread::vm_operation(); 401 log_debug(safepoint)("Entering safepoint region: %s", 402 (op != NULL) ? op->name() : "no vm operation"); 403 } 404 405 RuntimeService::record_safepoint_synchronized(); 406 if (PrintSafepointStatistics) { 407 update_statistics_on_sync_end(os::javaTimeNanos()); 408 } 409 410 // Call stuff that needs to be run when a safepoint is just about to be completed 411 { 412 EventSafepointCleanup cleanup_event; 413 do_cleanup_tasks(); 414 if (cleanup_event.should_commit()) { 415 cleanup_event.set_safepointId(safepoint_counter()); 416 cleanup_event.commit(); 417 } 418 } 419 420 if (PrintSafepointStatistics) { 421 // Record how much time spend on the above cleanup tasks 422 update_statistics_on_cleanup_end(os::javaTimeNanos()); 423 } 424 if (begin_event.should_commit()) { 425 begin_event.set_safepointId(safepoint_counter()); 426 begin_event.set_totalThreadCount(nof_threads); 427 begin_event.set_jniCriticalThreadCount(_current_jni_active_count); 428 begin_event.commit(); 429 } 430 } 431 432 // Wake up all threads, so they are ready to resume execution after the safepoint 433 // operation has been carried out 434 void SafepointSynchronize::end() { 435 EventSafepointEnd event; 436 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id" 437 438 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 439 assert((_safepoint_counter & 0x1) == 1, "must be odd"); 440 _safepoint_counter ++; 441 // memory fence isn't required here since an odd _safepoint_counter 442 // value can do no harm and a fence is issued below anyway. 443 444 DEBUG_ONLY(Thread* myThread = Thread::current();) 445 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); 446 447 if (PrintSafepointStatistics) { 448 end_statistics(os::javaTimeNanos()); 449 } 450 451 #ifdef ASSERT 452 // A pending_exception cannot be installed during a safepoint. The threads 453 // may install an async exception after they come back from a safepoint into 454 // pending_exception after they unblock. But that should happen later. 455 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 456 assert (!(cur->has_pending_exception() && 457 cur->safepoint_state()->is_at_poll_safepoint()), 458 "safepoint installed a pending exception"); 459 } 460 #endif // ASSERT 461 462 if (PageArmed) { 463 // Make polling safepoint aware 464 os::make_polling_page_readable(); 465 PageArmed = 0 ; 466 } 467 468 // Remove safepoint check from interpreter 469 Interpreter::ignore_safepoints(); 470 471 { 472 MutexLocker mu(Safepoint_lock); 473 474 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 475 476 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method 477 // when they get restarted. 478 _state = _not_synchronized; 479 OrderAccess::fence(); 480 481 log_debug(safepoint)("Leaving safepoint region"); 482 483 // Start suspended threads 484 for(JavaThread *current = Threads::first(); current; current = current->next()) { 485 // A problem occurring on Solaris is when attempting to restart threads 486 // the first #cpus - 1 go well, but then the VMThread is preempted when we get 487 // to the next one (since it has been running the longest). We then have 488 // to wait for a cpu to become available before we can continue restarting 489 // threads. 490 // FIXME: This causes the performance of the VM to degrade when active and with 491 // large numbers of threads. Apparently this is due to the synchronous nature 492 // of suspending threads. 493 // 494 // TODO-FIXME: the comments above are vestigial and no longer apply. 495 // Furthermore, using solaris' schedctl in this particular context confers no benefit 496 if (VMThreadHintNoPreempt) { 497 os::hint_no_preempt(); 498 } 499 ThreadSafepointState* cur_state = current->safepoint_state(); 500 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); 501 cur_state->restart(); 502 assert(cur_state->is_running(), "safepoint state has not been reset"); 503 } 504 505 RuntimeService::record_safepoint_end(); 506 507 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads 508 // blocked in signal_thread_blocked 509 Threads_lock->unlock(); 510 511 } 512 #if INCLUDE_ALL_GCS 513 // If there are any concurrent GC threads resume them. 514 if (UseConcMarkSweepGC) { 515 ConcurrentMarkSweepThread::desynchronize(false); 516 } else if (UseG1GC) { 517 SuspendibleThreadSet::desynchronize(); 518 } 519 #endif // INCLUDE_ALL_GCS 520 // record this time so VMThread can keep track how much time has elapsed 521 // since last safepoint. 522 _end_of_last_safepoint = os::javaTimeMillis(); 523 524 if (event.should_commit()) { 525 event.set_safepointId(safepoint_id); 526 event.commit(); 527 } 528 } 529 530 bool SafepointSynchronize::is_cleanup_needed() { 531 // Need a safepoint if some inline cache buffers is non-empty 532 if (!InlineCacheBuffer::is_empty()) return true; 533 return false; 534 } 535 536 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) { 537 if (event.should_commit()) { 538 event.set_safepointId(SafepointSynchronize::safepoint_counter()); 539 event.set_name(name); 540 event.commit(); 541 } 542 } 543 544 // Various cleaning tasks that should be done periodically at safepoints 545 void SafepointSynchronize::do_cleanup_tasks() { 546 { 547 const char* name = "deflating idle monitors"; 548 EventSafepointCleanupTask event; 549 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 550 ObjectSynchronizer::deflate_idle_monitors(); 551 event_safepoint_cleanup_task_commit(event, name); 552 } 553 554 { 555 const char* name = "updating inline caches"; 556 EventSafepointCleanupTask event; 557 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 558 InlineCacheBuffer::update_inline_caches(); 559 event_safepoint_cleanup_task_commit(event, name); 560 } 561 { 562 const char* name = "compilation policy safepoint handler"; 563 EventSafepointCleanupTask event; 564 TraceTime timer("compilation policy safepoint handler", TRACETIME_LOG(Info, safepoint, cleanup)); 565 CompilationPolicy::policy()->do_safepoint_work(); 566 event_safepoint_cleanup_task_commit(event, name); 567 } 568 569 { 570 const char* name = "mark nmethods"; 571 EventSafepointCleanupTask event; 572 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 573 NMethodSweeper::mark_active_nmethods(); 574 event_safepoint_cleanup_task_commit(event, name); 575 } 576 577 if (SymbolTable::needs_rehashing()) { 578 const char* name = "rehashing symbol table"; 579 EventSafepointCleanupTask event; 580 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 581 SymbolTable::rehash_table(); 582 event_safepoint_cleanup_task_commit(event, name); 583 } 584 585 if (StringTable::needs_rehashing()) { 586 const char* name = "rehashing string table"; 587 EventSafepointCleanupTask event; 588 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 589 StringTable::rehash_table(); 590 event_safepoint_cleanup_task_commit(event, name); 591 } 592 593 { 594 // CMS delays purging the CLDG until the beginning of the next safepoint and to 595 // make sure concurrent sweep is done 596 const char* name = "purging class loader data graph"; 597 EventSafepointCleanupTask event; 598 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 599 ClassLoaderDataGraph::purge_if_needed(); 600 event_safepoint_cleanup_task_commit(event, name); 601 } 602 } 603 604 605 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) { 606 switch(state) { 607 case _thread_in_native: 608 // native threads are safe if they have no java stack or have walkable stack 609 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); 610 611 // blocked threads should have already have walkable stack 612 case _thread_blocked: 613 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); 614 return true; 615 616 default: 617 return false; 618 } 619 } 620 621 622 // See if the thread is running inside a lazy critical native and 623 // update the thread critical count if so. Also set a suspend flag to 624 // cause the native wrapper to return into the JVM to do the unlock 625 // once the native finishes. 626 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) { 627 if (state == _thread_in_native && 628 thread->has_last_Java_frame() && 629 thread->frame_anchor()->walkable()) { 630 // This thread might be in a critical native nmethod so look at 631 // the top of the stack and increment the critical count if it 632 // is. 633 frame wrapper_frame = thread->last_frame(); 634 CodeBlob* stub_cb = wrapper_frame.cb(); 635 if (stub_cb != NULL && 636 stub_cb->is_nmethod() && 637 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) { 638 // A thread could potentially be in a critical native across 639 // more than one safepoint, so only update the critical state on 640 // the first one. When it returns it will perform the unlock. 641 if (!thread->do_critical_native_unlock()) { 642 #ifdef ASSERT 643 if (!thread->in_critical()) { 644 GCLocker::increment_debug_jni_lock_count(); 645 } 646 #endif 647 thread->enter_critical(); 648 // Make sure the native wrapper calls back on return to 649 // perform the needed critical unlock. 650 thread->set_critical_native_unlock(); 651 } 652 } 653 } 654 } 655 656 657 658 // ------------------------------------------------------------------------------------------------------- 659 // Implementation of Safepoint callback point 660 661 void SafepointSynchronize::block(JavaThread *thread) { 662 assert(thread != NULL, "thread must be set"); 663 assert(thread->is_Java_thread(), "not a Java thread"); 664 665 // Threads shouldn't block if they are in the middle of printing, but... 666 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); 667 668 // Only bail from the block() call if the thread is gone from the 669 // thread list; starting to exit should still block. 670 if (thread->is_terminated()) { 671 // block current thread if we come here from native code when VM is gone 672 thread->block_if_vm_exited(); 673 674 // otherwise do nothing 675 return; 676 } 677 678 JavaThreadState state = thread->thread_state(); 679 thread->frame_anchor()->make_walkable(thread); 680 681 // Check that we have a valid thread_state at this point 682 switch(state) { 683 case _thread_in_vm_trans: 684 case _thread_in_Java: // From compiled code 685 686 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case, 687 // we pretend we are still in the VM. 688 thread->set_thread_state(_thread_in_vm); 689 690 if (is_synchronizing()) { 691 Atomic::inc (&TryingToBlock) ; 692 } 693 694 // We will always be holding the Safepoint_lock when we are examine the state 695 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and 696 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code 697 Safepoint_lock->lock_without_safepoint_check(); 698 if (is_synchronizing()) { 699 // Decrement the number of threads to wait for and signal vm thread 700 assert(_waiting_to_block > 0, "sanity check"); 701 _waiting_to_block--; 702 thread->safepoint_state()->set_has_called_back(true); 703 704 DEBUG_ONLY(thread->set_visited_for_critical_count(true)); 705 if (thread->in_critical()) { 706 // Notice that this thread is in a critical section 707 increment_jni_active_count(); 708 } 709 710 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread 711 if (_waiting_to_block == 0) { 712 Safepoint_lock->notify_all(); 713 } 714 } 715 716 // We transition the thread to state _thread_blocked here, but 717 // we can't do our usual check for external suspension and then 718 // self-suspend after the lock_without_safepoint_check() call 719 // below because we are often called during transitions while 720 // we hold different locks. That would leave us suspended while 721 // holding a resource which results in deadlocks. 722 thread->set_thread_state(_thread_blocked); 723 Safepoint_lock->unlock(); 724 725 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during 726 // the entire safepoint, the threads will all line up here during the safepoint. 727 Threads_lock->lock_without_safepoint_check(); 728 // restore original state. This is important if the thread comes from compiled code, so it 729 // will continue to execute with the _thread_in_Java state. 730 thread->set_thread_state(state); 731 Threads_lock->unlock(); 732 break; 733 734 case _thread_in_native_trans: 735 case _thread_blocked_trans: 736 case _thread_new_trans: 737 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) { 738 thread->print_thread_state(); 739 fatal("Deadlock in safepoint code. " 740 "Should have called back to the VM before blocking."); 741 } 742 743 // We transition the thread to state _thread_blocked here, but 744 // we can't do our usual check for external suspension and then 745 // self-suspend after the lock_without_safepoint_check() call 746 // below because we are often called during transitions while 747 // we hold different locks. That would leave us suspended while 748 // holding a resource which results in deadlocks. 749 thread->set_thread_state(_thread_blocked); 750 751 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence, 752 // the safepoint code might still be waiting for it to block. We need to change the state here, 753 // so it can see that it is at a safepoint. 754 755 // Block until the safepoint operation is completed. 756 Threads_lock->lock_without_safepoint_check(); 757 758 // Restore state 759 thread->set_thread_state(state); 760 761 Threads_lock->unlock(); 762 break; 763 764 default: 765 fatal("Illegal threadstate encountered: %d", state); 766 } 767 768 // Check for pending. async. exceptions or suspends - except if the 769 // thread was blocked inside the VM. has_special_runtime_exit_condition() 770 // is called last since it grabs a lock and we only want to do that when 771 // we must. 772 // 773 // Note: we never deliver an async exception at a polling point as the 774 // compiler may not have an exception handler for it. The polling 775 // code will notice the async and deoptimize and the exception will 776 // be delivered. (Polling at a return point is ok though). Sure is 777 // a lot of bother for a deprecated feature... 778 // 779 // We don't deliver an async exception if the thread state is 780 // _thread_in_native_trans so JNI functions won't be called with 781 // a surprising pending exception. If the thread state is going back to java, 782 // async exception is checked in check_special_condition_for_native_trans(). 783 784 if (state != _thread_blocked_trans && 785 state != _thread_in_vm_trans && 786 thread->has_special_runtime_exit_condition()) { 787 thread->handle_special_runtime_exit_condition( 788 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans)); 789 } 790 } 791 792 // ------------------------------------------------------------------------------------------------------ 793 // Exception handlers 794 795 796 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { 797 assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); 798 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); 799 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); 800 801 if (ShowSafepointMsgs) { 802 tty->print("handle_polling_page_exception: "); 803 } 804 805 if (PrintSafepointStatistics) { 806 inc_page_trap_count(); 807 } 808 809 ThreadSafepointState* state = thread->safepoint_state(); 810 811 state->handle_polling_page_exception(); 812 } 813 814 815 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) { 816 if (!timeout_error_printed) { 817 timeout_error_printed = true; 818 // Print out the thread info which didn't reach the safepoint for debugging 819 // purposes (useful when there are lots of threads in the debugger). 820 tty->cr(); 821 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:"); 822 if (reason == _spinning_timeout) { 823 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); 824 } else if (reason == _blocking_timeout) { 825 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop."); 826 } 827 828 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); 829 ThreadSafepointState *cur_state; 830 ResourceMark rm; 831 for(JavaThread *cur_thread = Threads::first(); cur_thread; 832 cur_thread = cur_thread->next()) { 833 cur_state = cur_thread->safepoint_state(); 834 835 if (cur_thread->thread_state() != _thread_blocked && 836 ((reason == _spinning_timeout && cur_state->is_running()) || 837 (reason == _blocking_timeout && !cur_state->has_called_back()))) { 838 tty->print("# "); 839 cur_thread->print(); 840 tty->cr(); 841 } 842 } 843 tty->print_cr("# SafepointSynchronize::begin: (End of list)"); 844 } 845 846 // To debug the long safepoint, specify both DieOnSafepointTimeout & 847 // ShowMessageBoxOnError. 848 if (DieOnSafepointTimeout) { 849 VM_Operation *op = VMThread::vm_operation(); 850 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", 851 SafepointTimeoutDelay, 852 op != NULL ? op->name() : "no vm operation"); 853 } 854 } 855 856 857 // ------------------------------------------------------------------------------------------------------- 858 // Implementation of ThreadSafepointState 859 860 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { 861 _thread = thread; 862 _type = _running; 863 _has_called_back = false; 864 _at_poll_safepoint = false; 865 } 866 867 void ThreadSafepointState::create(JavaThread *thread) { 868 ThreadSafepointState *state = new ThreadSafepointState(thread); 869 thread->set_safepoint_state(state); 870 } 871 872 void ThreadSafepointState::destroy(JavaThread *thread) { 873 if (thread->safepoint_state()) { 874 delete(thread->safepoint_state()); 875 thread->set_safepoint_state(NULL); 876 } 877 } 878 879 void ThreadSafepointState::examine_state_of_thread() { 880 assert(is_running(), "better be running or just have hit safepoint poll"); 881 882 JavaThreadState state = _thread->thread_state(); 883 884 // Save the state at the start of safepoint processing. 885 _orig_thread_state = state; 886 887 // Check for a thread that is suspended. Note that thread resume tries 888 // to grab the Threads_lock which we own here, so a thread cannot be 889 // resumed during safepoint synchronization. 890 891 // We check to see if this thread is suspended without locking to 892 // avoid deadlocking with a third thread that is waiting for this 893 // thread to be suspended. The third thread can notice the safepoint 894 // that we're trying to start at the beginning of its SR_lock->wait() 895 // call. If that happens, then the third thread will block on the 896 // safepoint while still holding the underlying SR_lock. We won't be 897 // able to get the SR_lock and we'll deadlock. 898 // 899 // We don't need to grab the SR_lock here for two reasons: 900 // 1) The suspend flags are both volatile and are set with an 901 // Atomic::cmpxchg() call so we should see the suspended 902 // state right away. 903 // 2) We're being called from the safepoint polling loop; if 904 // we don't see the suspended state on this iteration, then 905 // we'll come around again. 906 // 907 bool is_suspended = _thread->is_ext_suspended(); 908 if (is_suspended) { 909 roll_forward(_at_safepoint); 910 return; 911 } 912 913 // Some JavaThread states have an initial safepoint state of 914 // running, but are actually at a safepoint. We will happily 915 // agree and update the safepoint state here. 916 if (SafepointSynchronize::safepoint_safe(_thread, state)) { 917 SafepointSynchronize::check_for_lazy_critical_native(_thread, state); 918 roll_forward(_at_safepoint); 919 return; 920 } 921 922 if (state == _thread_in_vm) { 923 roll_forward(_call_back); 924 return; 925 } 926 927 // All other thread states will continue to run until they 928 // transition and self-block in state _blocked 929 // Safepoint polling in compiled code causes the Java threads to do the same. 930 // Note: new threads may require a malloc so they must be allowed to finish 931 932 assert(is_running(), "examine_state_of_thread on non-running thread"); 933 return; 934 } 935 936 // Returns true is thread could not be rolled forward at present position. 937 void ThreadSafepointState::roll_forward(suspend_type type) { 938 _type = type; 939 940 switch(_type) { 941 case _at_safepoint: 942 SafepointSynchronize::signal_thread_at_safepoint(); 943 DEBUG_ONLY(_thread->set_visited_for_critical_count(true)); 944 if (_thread->in_critical()) { 945 // Notice that this thread is in a critical section 946 SafepointSynchronize::increment_jni_active_count(); 947 } 948 break; 949 950 case _call_back: 951 set_has_called_back(false); 952 break; 953 954 case _running: 955 default: 956 ShouldNotReachHere(); 957 } 958 } 959 960 void ThreadSafepointState::restart() { 961 switch(type()) { 962 case _at_safepoint: 963 case _call_back: 964 break; 965 966 case _running: 967 default: 968 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d", 969 p2i(_thread), _type); 970 _thread->print(); 971 ShouldNotReachHere(); 972 } 973 _type = _running; 974 set_has_called_back(false); 975 } 976 977 978 void ThreadSafepointState::print_on(outputStream *st) const { 979 const char *s = NULL; 980 981 switch(_type) { 982 case _running : s = "_running"; break; 983 case _at_safepoint : s = "_at_safepoint"; break; 984 case _call_back : s = "_call_back"; break; 985 default: 986 ShouldNotReachHere(); 987 } 988 989 st->print_cr("Thread: " INTPTR_FORMAT 990 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", 991 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back, 992 _at_poll_safepoint); 993 994 _thread->print_thread_state_on(st); 995 } 996 997 // --------------------------------------------------------------------------------------------------------------------- 998 999 // Block the thread at the safepoint poll or poll return. 1000 void ThreadSafepointState::handle_polling_page_exception() { 1001 1002 // Check state. block() will set thread state to thread_in_vm which will 1003 // cause the safepoint state _type to become _call_back. 1004 assert(type() == ThreadSafepointState::_running, 1005 "polling page exception on thread not running state"); 1006 1007 // Step 1: Find the nmethod from the return address 1008 if (ShowSafepointMsgs && Verbose) { 1009 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc())); 1010 } 1011 address real_return_addr = thread()->saved_exception_pc(); 1012 1013 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 1014 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod"); 1015 CompiledMethod* nm = (CompiledMethod*)cb; 1016 1017 // Find frame of caller 1018 frame stub_fr = thread()->last_frame(); 1019 CodeBlob* stub_cb = stub_fr.cb(); 1020 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 1021 RegisterMap map(thread(), true); 1022 frame caller_fr = stub_fr.sender(&map); 1023 1024 // Should only be poll_return or poll 1025 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 1026 1027 // This is a poll immediately before a return. The exception handling code 1028 // has already had the effect of causing the return to occur, so the execution 1029 // will continue immediately after the call. In addition, the oopmap at the 1030 // return point does not mark the return value as an oop (if it is), so 1031 // it needs a handle here to be updated. 1032 if( nm->is_at_poll_return(real_return_addr) ) { 1033 ResourceMark rm; 1034 // See if return type is an oop. 1035 Method* method = nm->method(); 1036 bool return_oop = method->is_returning_oop(); 1037 1038 GrowableArray<Handle> return_values; 1039 ValueKlass* vk = NULL; 1040 if (!return_oop && method->is_returning_vt()) { 1041 // We're at a safepoint at the return of a method that returns 1042 // multiple values. We must make sure we preserve the oop values 1043 // across the safepoint. 1044 vk = ValueKlass::returned_value_type(map); 1045 assert(vk == NULL || vk == method->returned_value_type(thread()) || 1046 method->returned_value_type(thread()) == SystemDictionary::___Value_klass(), "Bad value klass"); 1047 if (vk != NULL && !vk->save_oop_results(map, return_values)) { 1048 return_oop = true; 1049 vk = NULL; 1050 } 1051 } 1052 1053 if (return_oop) { 1054 // The oop result has been saved on the stack together with all 1055 // the other registers. In order to preserve it over GCs we need 1056 // to keep it in a handle. 1057 oop result = caller_fr.saved_oop_result(&map); 1058 assert(result == NULL || result->is_oop(), "must be oop"); 1059 return_values.push(Handle(thread(), result)); 1060 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 1061 } 1062 1063 // Block the thread 1064 SafepointSynchronize::block(thread()); 1065 1066 // restore oop result, if any 1067 if (return_oop) { 1068 assert(return_values.length() == 1, "only one return value"); 1069 caller_fr.set_saved_oop_result(&map, return_values.pop()()); 1070 } else if (vk != NULL) { 1071 vk->restore_oop_results(map, return_values); 1072 } 1073 } 1074 1075 // This is a safepoint poll. Verify the return address and block. 1076 else { 1077 set_at_poll_safepoint(true); 1078 1079 // verify the blob built the "return address" correctly 1080 assert(real_return_addr == caller_fr.pc(), "must match"); 1081 1082 // Block the thread 1083 SafepointSynchronize::block(thread()); 1084 set_at_poll_safepoint(false); 1085 1086 // If we have a pending async exception deoptimize the frame 1087 // as otherwise we may never deliver it. 1088 if (thread()->has_async_condition()) { 1089 ThreadInVMfromJavaNoAsyncException __tiv(thread()); 1090 Deoptimization::deoptimize_frame(thread(), caller_fr.id()); 1091 } 1092 1093 // If an exception has been installed we must check for a pending deoptimization 1094 // Deoptimize frame if exception has been thrown. 1095 1096 if (thread()->has_pending_exception() ) { 1097 RegisterMap map(thread(), true); 1098 frame caller_fr = stub_fr.sender(&map); 1099 if (caller_fr.is_deoptimized_frame()) { 1100 // The exception patch will destroy registers that are still 1101 // live and will be needed during deoptimization. Defer the 1102 // Async exception should have deferred the exception until the 1103 // next safepoint which will be detected when we get into 1104 // the interpreter so if we have an exception now things 1105 // are messed up. 1106 1107 fatal("Exception installed and deoptimization is pending"); 1108 } 1109 } 1110 } 1111 } 1112 1113 1114 // 1115 // Statistics & Instrumentations 1116 // 1117 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; 1118 jlong SafepointSynchronize::_safepoint_begin_time = 0; 1119 int SafepointSynchronize::_cur_stat_index = 0; 1120 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; 1121 julong SafepointSynchronize::_coalesced_vmop_count = 0; 1122 jlong SafepointSynchronize::_max_sync_time = 0; 1123 jlong SafepointSynchronize::_max_vmop_time = 0; 1124 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f; 1125 1126 static jlong cleanup_end_time = 0; 1127 static bool need_to_track_page_armed_status = false; 1128 static bool init_done = false; 1129 1130 // Helper method to print the header. 1131 static void print_header() { 1132 tty->print(" vmop " 1133 "[threads: total initially_running wait_to_block] "); 1134 tty->print("[time: spin block sync cleanup vmop] "); 1135 1136 // no page armed status printed out if it is always armed. 1137 if (need_to_track_page_armed_status) { 1138 tty->print("page_armed "); 1139 } 1140 1141 tty->print_cr("page_trap_count"); 1142 } 1143 1144 void SafepointSynchronize::deferred_initialize_stat() { 1145 if (init_done) return; 1146 1147 // If PrintSafepointStatisticsTimeout is specified, the statistics data will 1148 // be printed right away, in which case, _safepoint_stats will regress to 1149 // a single element array. Otherwise, it is a circular ring buffer with default 1150 // size of PrintSafepointStatisticsCount. 1151 int stats_array_size; 1152 if (PrintSafepointStatisticsTimeout > 0) { 1153 stats_array_size = 1; 1154 PrintSafepointStatistics = true; 1155 } else { 1156 stats_array_size = PrintSafepointStatisticsCount; 1157 } 1158 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size 1159 * sizeof(SafepointStats), mtInternal); 1160 guarantee(_safepoint_stats != NULL, 1161 "not enough memory for safepoint instrumentation data"); 1162 1163 if (DeferPollingPageLoopCount >= 0) { 1164 need_to_track_page_armed_status = true; 1165 } 1166 init_done = true; 1167 } 1168 1169 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { 1170 assert(init_done, "safepoint statistics array hasn't been initialized"); 1171 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1172 1173 spstat->_time_stamp = _ts_of_current_safepoint; 1174 1175 VM_Operation *op = VMThread::vm_operation(); 1176 spstat->_vmop_type = (op != NULL ? op->type() : -1); 1177 if (op != NULL) { 1178 _safepoint_reasons[spstat->_vmop_type]++; 1179 } 1180 1181 spstat->_nof_total_threads = nof_threads; 1182 spstat->_nof_initial_running_threads = nof_running; 1183 spstat->_nof_threads_hit_page_trap = 0; 1184 1185 // Records the start time of spinning. The real time spent on spinning 1186 // will be adjusted when spin is done. Same trick is applied for time 1187 // spent on waiting for threads to block. 1188 if (nof_running != 0) { 1189 spstat->_time_to_spin = os::javaTimeNanos(); 1190 } else { 1191 spstat->_time_to_spin = 0; 1192 } 1193 } 1194 1195 void SafepointSynchronize::update_statistics_on_spin_end() { 1196 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1197 1198 jlong cur_time = os::javaTimeNanos(); 1199 1200 spstat->_nof_threads_wait_to_block = _waiting_to_block; 1201 if (spstat->_nof_initial_running_threads != 0) { 1202 spstat->_time_to_spin = cur_time - spstat->_time_to_spin; 1203 } 1204 1205 if (need_to_track_page_armed_status) { 1206 spstat->_page_armed = (PageArmed == 1); 1207 } 1208 1209 // Records the start time of waiting for to block. Updated when block is done. 1210 if (_waiting_to_block != 0) { 1211 spstat->_time_to_wait_to_block = cur_time; 1212 } else { 1213 spstat->_time_to_wait_to_block = 0; 1214 } 1215 } 1216 1217 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { 1218 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1219 1220 if (spstat->_nof_threads_wait_to_block != 0) { 1221 spstat->_time_to_wait_to_block = end_time - 1222 spstat->_time_to_wait_to_block; 1223 } 1224 1225 // Records the end time of sync which will be used to calculate the total 1226 // vm operation time. Again, the real time spending in syncing will be deducted 1227 // from the start of the sync time later when end_statistics is called. 1228 spstat->_time_to_sync = end_time - _safepoint_begin_time; 1229 if (spstat->_time_to_sync > _max_sync_time) { 1230 _max_sync_time = spstat->_time_to_sync; 1231 } 1232 1233 spstat->_time_to_do_cleanups = end_time; 1234 } 1235 1236 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) { 1237 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1238 1239 // Record how long spent in cleanup tasks. 1240 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups; 1241 1242 cleanup_end_time = end_time; 1243 } 1244 1245 void SafepointSynchronize::end_statistics(jlong vmop_end_time) { 1246 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1247 1248 // Update the vm operation time. 1249 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time; 1250 if (spstat->_time_to_exec_vmop > _max_vmop_time) { 1251 _max_vmop_time = spstat->_time_to_exec_vmop; 1252 } 1253 // Only the sync time longer than the specified 1254 // PrintSafepointStatisticsTimeout will be printed out right away. 1255 // By default, it is -1 meaning all samples will be put into the list. 1256 if ( PrintSafepointStatisticsTimeout > 0) { 1257 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) { 1258 print_statistics(); 1259 } 1260 } else { 1261 // The safepoint statistics will be printed out when the _safepoin_stats 1262 // array fills up. 1263 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) { 1264 print_statistics(); 1265 _cur_stat_index = 0; 1266 } else { 1267 _cur_stat_index++; 1268 } 1269 } 1270 } 1271 1272 void SafepointSynchronize::print_statistics() { 1273 SafepointStats* sstats = _safepoint_stats; 1274 1275 for (int index = 0; index <= _cur_stat_index; index++) { 1276 if (index % 30 == 0) { 1277 print_header(); 1278 } 1279 sstats = &_safepoint_stats[index]; 1280 tty->print("%.3f: ", sstats->_time_stamp); 1281 tty->print("%-26s [" 1282 INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15) 1283 " ] ", 1284 sstats->_vmop_type == -1 ? "no vm operation" : 1285 VM_Operation::name(sstats->_vmop_type), 1286 sstats->_nof_total_threads, 1287 sstats->_nof_initial_running_threads, 1288 sstats->_nof_threads_wait_to_block); 1289 // "/ MICROUNITS " is to convert the unit from nanos to millis. 1290 tty->print(" [" 1291 INT64_FORMAT_W(6) INT64_FORMAT_W(6) 1292 INT64_FORMAT_W(6) INT64_FORMAT_W(6) 1293 INT64_FORMAT_W(6) " ] ", 1294 sstats->_time_to_spin / MICROUNITS, 1295 sstats->_time_to_wait_to_block / MICROUNITS, 1296 sstats->_time_to_sync / MICROUNITS, 1297 sstats->_time_to_do_cleanups / MICROUNITS, 1298 sstats->_time_to_exec_vmop / MICROUNITS); 1299 1300 if (need_to_track_page_armed_status) { 1301 tty->print(INT32_FORMAT " ", sstats->_page_armed); 1302 } 1303 tty->print_cr(INT32_FORMAT " ", sstats->_nof_threads_hit_page_trap); 1304 } 1305 } 1306 1307 // This method will be called when VM exits. It will first call 1308 // print_statistics to print out the rest of the sampling. Then 1309 // it tries to summarize the sampling. 1310 void SafepointSynchronize::print_stat_on_exit() { 1311 if (_safepoint_stats == NULL) return; 1312 1313 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1314 1315 // During VM exit, end_statistics may not get called and in that 1316 // case, if the sync time is less than PrintSafepointStatisticsTimeout, 1317 // don't print it out. 1318 // Approximate the vm op time. 1319 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = 1320 os::javaTimeNanos() - cleanup_end_time; 1321 1322 if ( PrintSafepointStatisticsTimeout < 0 || 1323 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) { 1324 print_statistics(); 1325 } 1326 tty->cr(); 1327 1328 // Print out polling page sampling status. 1329 if (!need_to_track_page_armed_status) { 1330 tty->print_cr("Polling page always armed"); 1331 } else { 1332 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n", 1333 DeferPollingPageLoopCount); 1334 } 1335 1336 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 1337 if (_safepoint_reasons[index] != 0) { 1338 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index), 1339 _safepoint_reasons[index]); 1340 } 1341 } 1342 1343 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint", 1344 _coalesced_vmop_count); 1345 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms", 1346 _max_sync_time / MICROUNITS); 1347 tty->print_cr("Maximum vm operation time (except for Exit VM operation) " 1348 INT64_FORMAT_W(5) " ms", 1349 _max_vmop_time / MICROUNITS); 1350 } 1351 1352 // ------------------------------------------------------------------------------------------------ 1353 // Non-product code 1354 1355 #ifndef PRODUCT 1356 1357 void SafepointSynchronize::print_state() { 1358 if (_state == _not_synchronized) { 1359 tty->print_cr("not synchronized"); 1360 } else if (_state == _synchronizing || _state == _synchronized) { 1361 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : 1362 "synchronized"); 1363 1364 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 1365 cur->safepoint_state()->print(); 1366 } 1367 } 1368 } 1369 1370 void SafepointSynchronize::safepoint_msg(const char* format, ...) { 1371 if (ShowSafepointMsgs) { 1372 va_list ap; 1373 va_start(ap, format); 1374 tty->vprint_cr(format, ap); 1375 va_end(ap); 1376 } 1377 } 1378 1379 #endif // !PRODUCT